Eighty-five percent of the women in the United States experience hot flashes of some kind as they approach menopause and for the first year or two after their periods stop. Between 20 and 50% of women continue to have them for many more years. A hot flash is characterized by a sudden, intense, hot feeling on the face and upper body. Often the hot flash can be preceded or accompanied by a rapid heartbeat and sweating, nausea, dizziness, anxiety, headache, weakness, or a feeling of suffocation. Some women experience a general, overall uneasy feeling just before the hot flash. A hot flash is generally followed by a flush, leaving the sufferer reddened and perspiring. High intensity hot flashes can result in the sufferer becoming soaked in perspiration. Lower intensity flashes cause merely produce a moist upper lip. A chill often precedes the flash, but can also occur at the conclusion of the flash. When hot flashes occur during the night, they sufferer can't sleep, resulting in poor concentration, memory problems, irritability and exhaustion during the day.
Hot flashes are often due to the hormonal changes of menopause, but can also be affected by lifestyle and medications. The exact cause of hot flashes is not currently known. Some theories suggest that hot flashes are due to a drop in the body's level of female hormones called estrogens. A diminished level of estrogen has a direct effect on the hypothalamus, the part of the brain responsible for controlling appetite, sleep cycles, sex hormones, and body temperature. The body responds to reduced levels of estrogen by increasing release of neurotransmitters from the hypothalamus and these increases in epinephrine, norepinephrine, prostaglandin and serotonin cause the heart to pump faster, the blood vessels in skin to dilate and sweat glands release sweat. Some people's skin temperature can rise six degrees Centigrade during a hot flash. Areas of dilation of blood vessels in the skin are particularly noticeable in those areas near the skin of the head, face, neck and chest. This skin dilation cause more blood to circulate in order to radiate off the heat. The sweat glands then release sweat to cool the body off even more. Once the blood vessels return to normal size, the sufferer feels cool again.
Around 85% of women suffer hot flashes during the years immediately before and after menopause, which occurs on average around the age of 51. Hot flashes can begin as early as 2 to 3 years prior to the last menstrual period, however. The hot flashes can last up to six months or go as long as after 15 years after the last menstrual period. On average, the hot flashes continue for two years. The frequency of episodes varies widely, from a few episodes a year to up to 20 episodes a day. Men can also have hot flashes if their levels of the male sex hormone testosterone drop suddenly and dramatically.
Both men and women can suffer from hot flashes as a side effect of cancer therapy. Certain drugs such as Tamoxifen (Nolvadex), which is used to treat breast cancer, as well as Lupron (Leuprolide) and Zoladex (Goserelin), which are employed in the therapy of prostate cancer, can lead to heat sensations. Bilateral orchiectomy for prostate cancer or testicular cancer also affects the hormone system so that patients can subsequently suffer from hot flashes. Especially in the case of cancer patients, hormone replacement therapy is often not advised, because there is a concern that cancer regrowth can be stimulated.
Symptoms that mimic hot flashes can occur in both men and women who have a tumor of the hypothalamus or pituitary gland, as well as with those who have suffered from certain serious infections, such as tuberculosis or HIV, those with alcoholism or those who suffer from thyroid disorders. Symptoms that are similar to hot flashes also can be a side effect of the food additive monosodium glutamate (MSG), or of certain medications, particularly nitroglycerin, nifedipine, niacin, vancomycin and calcitonin.
Most commonly, Hormone Replacement Therapy (HRT) is believed to be one of the most effective treatments available to reduce the onset of hot flashes. These hormones can be taken orally, intravenously, transdermally and/or topically, applied in a cream. However HRT has been associated with increased risk of heart disease as well as certain kinds of cancers.
In addition to hrt and the other medications noted above, several nonprescription dietary supplements or herbal remedies have been promoted as natural ways to prevent or treat hot flashes. A range of “natural” therapies on a herbal basis including black cohosh, phytoestrogens, flax seed, red clover, vitamin E (D. L. Barton et al., J. Clin. Oncol. 1998, 16: 495-500), ginseng and evening primrose oil have been advocated as possible medications (University of Wisconsin Medical School, online courses, “Alternatives for Menopausal Symptoms: A Review of the Evidence”; www.cme.wisc.edu/online/menopause). However, not all of these therapies are effective (K. I. Pritchard, The Oncologist, 2001, 6(4), 353-362).
Alternative medications to help decrease the intensity of hot flashes include clonidine, lofexidine, methyldopa and sertraline. Other medications, which have been suggested, are selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine hydrochloride (Prozac; C. Loprinzi; www.medicine-news.com/articles/pharma/misc/hotflash-es.html) and paroxetine hydrochloride (Paxil; V. Stearns et al., Ann. Oncol., 2000, 11:17-22) as well as venlafaxine hydrochloride (Effexor; C. L. Loprinzi et al., J. Clin. Oncol., 1998, 16: 2377-2381), which is a serotonin and norepinephrine reuptake inhibitor.
Low doses of megestrol acetate have also been shown to reduce the frequency of hot flashes in both men and women (Loprinzi et al., N. Engl. J. Med. 1994, 331:347-351). Chronic adrenal insufficiency and weight gain can be side effects. Transdermal clonidine has also been employed to reduce the frequency and severity of hot flashes (R. M. Goldberg et al., J. Clin. Onc. 1994, 12:155-158); R. M. Goldberg et al., J. Clin. Oncol. 1994, 12:155-158; L. R. Laufer, Obstet. Gynecol. 1982, 60:583-586). However, side effects such as drowsiness, fatigue, and symptoms of low blood pressure in some patients were observed.
A variety of treatments addressing hot flashes have been proposed. For example, US Publication No. 2004/0092519 to Pharmacia & Upjohn describes methods of treating or preventing hot flashes by administering effective dose of a compound selected from reboxetine, S,S-reboxetine, pharmaceutically acceptable salts thereof, derivatives thereof, or prodrugs thereof. U.S. Pat. No. 6,165,504 to Barr Labs describes methods for treating hot flashes and improving the quality of life of castrated prostatic cancer patients by administration of cyproterone acetate. US Publication No. 2004/0152733 describes the use of duloxetine for treatment of hot flashes. US Publication No. 2004/0092519 describes the use of reboxetine for treatment of symptoms of hormonal variation such as hot flashes. U.S. Pat. No. 6,395,757 describes administration of glycopyrrolate analogs for treating hot flashes. US Publication No. 2007/0281997 describes treatment of hot flashes in subject with prostate disorder such as prostate cancer being managed with androgen deprivation therapy using muscarinic receptor antagonists. US Publication No. 2007/0015786 describes treatment of hot flashes, impulse control disorders and personality change due to a general medical condition using selective norepinephrine reuptake inhibitors e.g. atomoxetine and racemic reboxetine. US Publication No. 2002/0016283 describes a method of treating symptoms of hormonal variation, including hot flashes, using tachykinin receptor antagonist. U.S. Pat. No. 6,310,098 describes a method of treating symptoms of hormonal variation including hot flashes by administration of a compound which is a ligand of the alpha-2-delta subunit of a voltage-gated calcium channel.
However, new treatments for prevention or reduction of symptoms associated with such endocrine disturbances are needed.